You can't make a mistake on the internet. Someone will find it and alert the rest of the world. Best Buy found that out when they inadvertently posted three previously unknown amiibos on its site.
There aren't many details other than a SKU and that they are compatible with Nintendo Switch's Zelda, found by reddit user Pokemiibomadness. Technically, all amiibos will work with Breath of the Wild, but Best Buy usually only lists the game if the amiibos is expected to unlock special content. The items say they were just announced for the Switch and more information would be coming soon.
Right now, the info has been pulled except for placeholder SKU info the amiibos, and items being listed as out of stock.
As for speculation on what amiibos they could be, two of these could be unlocks for the currently inaccessible Skyward Sword and Majora's Mask Fierce Deity costumes. Footage of both exist in the wild (so to speak), but no one has yet found a way to properly unlock them.
Of course, until Nintendo actually gives up the goods, it is all just speculation at this point.